For the fabrication of semiconductor devices and various other high-tech devices, such as micro/nano machines, nanometer-order etching and thin-film deposition must be achieved with high accuracy. Therefore, in a plasma process for such processing, it is essential to monitor the process on an actual wafer. To accomplish this purpose, there is already proposed an on-wafer monitoring system comprising a plasma monitoring sensor, a data transmit/receive processing circuit with optical interconnection, and a power supply which are fabricated in integral fashion on a silicon substrate (Refer to Japanese Unexamined Patent Publication 2003-282546).
Plasma process monitoring is performed by placing this system in a processing position within a plasma apparatus and by generating a plasma in this condition. That is, the on-wafer monitoring system is placed within the plasma apparatus in place of a semiconductor wafer to be processed actually, and the plasma process is monitored by simulating the process.
However, the on-wafer monitoring system described in JPA 2003-282546 is one that checks the surface condition of a wafer at the end of the process (for example, etching) or at an intermediate point during the process, and not one that keeps track of the wafer condition that varies as the process progresses. Furthermore, the monitoring is no more than the simulation of the plasma process, and the system does not provide the real-time monitoring of a semiconductor wafer actually being processed.
With increasing miniaturization of semiconductor devices, it has become increasingly important to control plasma processes in real time and with high accuracy. Further, detecting the endpoint of a process such as etching in real time is extremely important in order to achieve fine feature processing with high accuracy and high yield. However, with the above-described system, neither the real-time monitoring of the plasma process nor the real-time detection of the process endpoint can be accomplished.